The lipid composition of rat-liver mitochondria, fluffy layer and microsomes

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Abstract
The lipids of rat-liver mitochondria, microsomes and fluffy layer have been separated by silicic acid chromatography and the fatty acid composition of each fraction has been measured. On a weight basis 26% of the mitochondria was lipid, whereas the fluffy layer contained 33% and the microsomes 55%. Lecithin and kephalin were present in the mitochondria in almost equal amounts (each about 38% of the total phospholipid), whereas there was twice as much lecithin as kephalin in the microsomes (lecithin 60% of total phospholipid, kephalin about 30%). The fluffy layer had quantities of lecithin and kephalin intermediate between those of the mitochondria and the microsomes. Cardiolipin was concentrated in the mitochondria to some 3.5 times that found in the whole cell. Kephalins had a higher proportion of arachidonic acid and docosahexaenoic acid than had other lipids. Thus, as the proportion of kephalins to lecithins in the mitochondria is higher than that in the microsomes, the mitochondria contain a higher proportion of these polyunsaturated fatty acids. The proportions of fatty acids in the lipid classes of mitochondria, fluffy layer and microsomes are presented.